Linear belt actuator

ABSTRACT

The invention concerns a linear actuator capable of transmitting tractive forces as well as thrust forces and operating then as a rigid single-piece rod. The invention is characterised in that it comprises two identical actuating belts ( 1, 1 ′) with notches on each of their sides ( 10, 10′; 11, 11 ′) and provided on one first side ( 10, 10 ′) with uniformly spaced blocks ( 2, 2 ′) which mesh with drive members ( 3 ) such that the two actuating belts ( 1, 1 ′) are independent upstream of the drive members ( 3 ), whereas downstream of said members, they are integrally assembled so as to define a section extending along a straight line wherein the linear actuator operates like a single-piece rigid rod.

[0001] The present invention relates to a linear actuator which cantransmit tractive forces and also thrust forces, in that case behavingas a unitary rigid bar

[0002] Thrust chains suitable for performing this function have alreadybeen proposed. Thrust chains of this type have already been described,for example, in the documents FR-1 297 285 and FR-2 061 884.

[0003] These chains are conventionally constituted by a series of linksarticulated to one another by means of pins that are arrangedtransversely.

[0004] Each link comprises two substantially parallel flanges which arepierced, respectively, by two holes for receiving the articulation pinsand each of which is equipped with an extension defining a fronttransverse active face and a rear transverse active face which arecaused to bear against the rear and front transverse active faces,respectively, of the flanges of the adjacent links when the portion ofchain of which the links in question form part extends along a straightline.

[0005] Thrust chains of this type are driven, in the region of a curvedend, by a device comprising a casing, a rotary pinion which has its axisparallel to the articulation pins of the links and is mounted in thecasing and on which the chain is wound, as well as idle rollers forguiding the links of the chain around the rotary pinion.

[0006] Thrust chains of this type can transmit tractive and thrustforces in a satisfactory manner in any direction, including upwards, buthave a fundamentally sophisticated configuration.

[0007] Moreover, these thrust chains are suitable purely for actuating“heavy” mechanical parts and, up to now, a similar device which isdesigned to enable changes in direction to be performed in smallautomatic mechanisms has never been proposed.

[0008] The object of the present invention is to fill this gap byproposing a linear actuator of the above-mentioned type which ischaracterized in that it comprises two identical actuating bolts whichare toothed on each of their faces and are provided, on a first of theirfares, with uniformly-spaced studs which mesh by means of drive membersin a manner such that the two actuating belts are independent upstreamof the drive members whereas, downstream of those members, they areassembled integrally so as to define a portion which extends along astraight line and in which the linear actuator behaves as a unitaryrigid bar.

[0009] These actuating belts are preferably made of a flexible,reinforced plastics in material and thus correspond to simple andinexpensive elements also having the advantage that they can bemanufactured by moulding in a single piece.

[0010] According to a preferred characteristic of the invention, thedrive members are constituted by a casing enclosing two rotary pinions,that is, a drive pinion and a driven pinion, which engage one anotherand drive two endless caterpillar-type bands mounted on one side and onthe other side of the actuating belts, respectively, and equipped ontheir outer faces with teeth which cooperate with the teeth situated onthe second faces of those belts and are fitted between those teeth so asto translate the belts whilst squeezing them against one another so thattheir facing studs engage one another.

[0011] According to the invention, the casing of the drive members alsocontains guide surfaces for the actuating belts, which guide surfacesare designed to enable the belts to bend in the region of the endlesscaterpillar-type bands in order to cause them to face one another sothat their respective studs can engage one another.

[0012] According to another characteristic of the invention, the studsof the actuating belts comprise two side faces as well as a fronttransverse active face and a rear transverse active face each having adouble curvature.

[0013] The front and rear transverse active faces of a stud of one ofthe actuating belts are caused to bear against the respective rear andfront transverse active faces, respectively, of two associated adjacentstuds of the other actuating belt when the two actuating belts areassembled integrally.

[0014] It is essential, in order for the linear actuator according tothe invention to be able to perform its function, that the linearportion defined by the two actuating belts when they are assembledintegrally should not include “voids” and, therefore, that the geometryof the actuating belts should be such that the shape and dimensions ofthe spaces between the studs should be identical to those of the studs.

[0015] According to another characteristic of the invention, the frontand rear transverse active faces of the studs comprise a double shoulderforming an abutment.

[0016] These shoulders prevent any transverse sliding of the adjacentstuds relative to one another when the two actuating belts are assembledintegrally.

[0017] According to another characteristic of the invention, the frontand rear transverse active faces of the studs are separated by asubstantially rectilinear, toothed longitudinal face.

[0018] The teeth of the longitudinal face of a stud of one of the beltsare caused to cooperate with corresponding teeth of the section of thefirst face of the other belt situated between the two studs associatedwith that stud, whilst being fitted between those teeth, when the twoactuating belts are assembled integrally.

[0019] As a result, in this position, the faring first faces of the twoactuating belts are intimately engaged over their entire length.

[0020] According to another characteristic of the invention, the tworotary pinions are extended coaxially by respective toothed extensionsof smaller diameter cooperating with respective idle auxiliary gears ofthe same diameter so as to drive the endless caterpillar-type bands.

[0021] According to the invention, the casing of the drive members mayalso advantageously contain at least a pair of positioning rollershaving axes substantially perpendicular to the axes of the rotarypinions and engaging on one side and on the other side of a linearportion of the actuator defined by the two integrally assembledactuating belts, against the side faces of the studs of those belts.

[0022] The characteristics of the linear actuator of the invention willbe described in greater detail with reference to the appended drawings,in which:

[0023]FIG. 1 is a diagram showing the linear actuator, in which theupper portion of the casing of the drive members has been removed,

[0024]FIG. 2 shows the two actuating belts,

[0025]FIG. 2a is a section through FIG. 2, taken in a plane indicatedschematically by the axis II-II,

[0026]FIG. 3 shows a detail of the two actuating belts,

[0027]FIG. 4 is a diagram showing the drive members, in which the upperportion of the casing of these members has been removed,

[0028]FIG. 5 is a section through FIG. 4, taken in a plane indicatedschematically by the axis V V, the actuating belts being positioned inthe drive members,

[0029]FIG. 6 is a section through FIG. 4 taken in a plane indicatedschematically by the axis VI VI, the actuating belts being positioned inthe drive members.

[0030] According to FIG. 1, the linear actuator comprises two identicalactuating belts 1, 1′ as well as drive members 3 which drive theactuating belts 1, 1′ so as to translate them in one direction or in theother in accordance with the double arrows A, B and B′.

[0031] In the lower portion of FIG. 1, that is, upstream of the drivemembers 3, the two actuating belts 1, 1′ are independent of one anotherwhereas, in the upper portion of FIG. 1, that is, downstream of thedrive members 3, the two belts 1, 1′ are assembled integrally so as todefine a portion which extends along a straight line and in which thelinear actuator behaves as a unitary rigid bar.

[0032] According to FIGS. 2, 2a and 3, the actuating belts 1, 1′ areprovided on each of their races 10, 11 and 10′, 11′ with identical teeth4, 4′ which are caused, respectively, to fit between associated teeth ina manner which will be described in greater detail below.

[0033] A first face 10, 10′ of the actuating belts 1 is also equippedwith uniformly-spaced studs 2, 2′ which are separated by toothedsections 5, 5′.

[0034] Each stud 2, 2′ comprises two side faces 6, 6′ as well as a fronttransverse active face 7, 7′ and a rear transverse active face 8, 8′having a double curvature.

[0035] The front and rear transverse active faces 7, 7′, 8, 8′ of thestuds 2, 2′ are separated by a substantially rectilinear toothedlongitudinal face 20, 20′.

[0036] As can be seen in particular in FIG. 3, the actuating belts 1, 1′have a geometry which is designed in a manner such that the shape anddimensions of the spaces between the studs 2, 2′ are identical to thoseof the studs.

[0037] According to FIG. 3, the front and rear transverse active faces7,7′, 8,8′ of the studs 2,2′ also comprise a double shoulder 9 formingan abutment the function of which will also bc explained below.

[0038] According to FIGS. 4, 5 and 6, the drive members 3 comprise acasing 12 containing two rotary pinions 13, 13′ of the same diameter andof axis X-X′, which engage one another.

[0039] According to FIG. 5, one of these pinions 13 is a drive pinionand is connected to a motor, not shown, by a drive axle 14 projectingfrom the casing 12, whereas the second rotary pinion 13′ is a drivenpinion.

[0040] According to FIGS. 4 and 5, the rotary pinions 13, 13′ areextended coaxially by respective extensions 15, 15′ equipped with teeth16, 16′ and having a smaller diameter.

[0041] According to FIG. 4, the toothed extensions 15, 15′ cooperate,respectively, with two idle auxiliary gears 17, 17′ of the same diameterand with parallel axes.

[0042] The rotary pinions 13, 13′ equipped with the toothed extensions15, 15′ and the auxiliary gears 17, 17′ also rotate two endlesscaterpillar-type bands 18, 18′ the inner faces of which art equipped,for this purpose, with teeth corresponding to the teeth of theextensions 15, 15′ and of the auxiliary gears 17, 17′.

[0043] These two endless bands 18, 18′ are caused to sandwich the twoactuating bolts 1, 1′ between them in order to guide the belts andtranslate them in one direction or in the other, according to thedirection of rotation of the drive pinion 13.

[0044] For this purpose, the outer faces of the two caterpillar-typeendless bands 18, 18′ also have teeth 21, 221′ which can engage theteeth 4, 4′ situated on the second faces 11, 11′ of the two actuatingbelts 1, 1′ in order to translate the belts in accordance with thearrows A, B and B′.

[0045] According to FIGS. 1 and 4, the casing 12 of the drive members 3also contains guide surfaces 19, 19′ fur the two actuating belts 1, 1′;the guide surfaces 19, 19′ cooperate with the longitudinal faces 20, 20′of the studs 2, 2′ of the belts in order to transfer the belts betweenthe endless caterpillar-type bands 18, 18′ or to disengage themtherefrom, by bending them.

[0046] According to FIG. 1, in the course of this transfer, when thedrive pinion 13 turns clockwise, the studs 2, 2′ of the two actuatingbelts 1, 1′ enter the casing 12 independently in the region of its sideedges, on one side and on the other side of the casing, and are thenguided so as to translate in its inner portion along the guide surfaces19, 19′, respectively, in the region of which guide surfaces 19, 19′ thebelts are subjected to bending such that they are situated facing oneanother before entering between the two endless caterpillar-type bands18, 18′.

[0047] In the region of these bands, the actuating belts 1, 1′ aresqueezed against one another so that the studs 2, 2′ mesh with oneanother and the two belts 1, 1′ are assembled integrally in a portionextending along a straight line.

[0048] For this purpose, the front and rear transverse active faces 7,7′, 8, 8′ of the studs 2, 2′ of one of the actuating belts 1, 1′ bear,respectively, against the rear and front transverse active faces 8′, 8,7′, 7 of the two associated adjacent studs 2′, 2 of the other actuatingbelt 1′, 1′ and the teeth 4, 4′ of the longitudinal faces 20, 20′ of thestuds 2, 2′ of one of the actuating belts 1, 1′ engage, respectively, inthe corresponding teeth of the respective section 5′ 5 of the otheractuating belt 1′, 1 separating the two associated adjacent studs 2′, 2,so that the two actuating belts are fitted together perfectly to definea unitary rigid bar.

[0049] In this position, the double abutment shoulders 9 provided on thetransverse active faces 7, 7′; 8, 8′ prevent any transverse sliding ofthe adjacent studs 2, 2′ relative to one another.

[0050] Naturally, when the drive pinion 13 turns anticlockwise, thedisplacement of the studs 2, 2′ of the two actuating belts 1, 1′ takesplace in the opposite direction, that is, the studs enter the casing 12fitted together and are separated at the level of the twocaterpillar-type endless bands 18, 18′.

[0051] Moreover, and according to FIGS. 4 and 6, the casing 12 alsoencloses two pairs of positioning rollers 22.

[0052] Each of these pairs is constituted by a combination of twopositioning rollers 22 ₁, 22 ₂ of axis Y-Y′ perpendicular to the axesX-X′ of the rotary pinions 13, 13′.

[0053] These positioning rollers 22 ₁, 22 ₂ engage against the sidefaces 6, 6′ of the studs 2, 2′ in order to ensure the correctpositioning of the actuating belts 1, 1′ when they are fitted together.

1-8 (canceled)
 9. Linear actuator which can transmit tractive forces andalso thrust forces and comprising, on the one hand, two identicalactuating belts (1, 1′) made of a flexible, and if necessary reinforced,plastics material, and having, on one face or an inner face thereof (10,10′) uniformly-spaced studs (2, 2′) separated by sections (5, 5′) andeach comprising two side faces (6, 6′) as well as a front transverseactive face (7, 7′) and a rear transverse active face (8, 8′) which areseparated by a substantially rectilinear longitudinal face (20, 20′)and, on the other hand, drive members (3) cooperating with teeth (4, 4′)situated on the other face or outer face (11, 11′) of the actuatingbelts (1, 1′) in order to translate the belts in a manner such that theyare independent upstream of those members (3) whereas, downstreamthereof, the facing studs (2, 2′) which are provided on the respectivefacing inner faces (10, 10′) of the two actuating belts (1, 1′) meshwith one another and the front and rear transverse active faces (7, 7′;8, 8′) of a stud (2, 2′) of one of the actuating belts (1, 1′) come tobear against the rear and front transverse active faces (8′, 8; 7′, 7),respectively, of two associated adjacent studs (2′, 2) of the otheractuating belt (1′, 1), defining a portion which extends along astraight line and in which the two actuating belts (1, 1′) are assembledintegrally, characterized in that: the shape and the dimensions of thespaces between the studs (2, 2′) of the actuating belts (1, 1′) areidentical to those of the studs so that the linear portion defined bythose belts (2, 2′) when they are assembled integrally comprises novoids, and the sections (5, 5′) of the respective inner faces (10, 10′)of the two actuating belts (1, 1′) which separate the studs (2, 2′), aswell as the longitudinal faces (20, 20′) of those studs (2, 2′), haveteeth (4, 4′), the teeth (4, 4′) of the longitudinal face (20, 20′) of astud (2, 2′) of one of the belts (1, 1′) cooperating with correspondingteeth (4′, 4) of the section (5′, 5) of the inner face (10′, 10) of theother belt (1′, 1) situated between the two studs (2′, 2) associatedwith that stud (2, 2′), whilst being fitted between those teeth, whenthe two actuating belts (1, 1′) are assembled integrally so that thelinear actuator behaves as a unitary rigid bar.
 10. Linear actuatoraccording to claim 9, characterized in that the teeth (4, 4′) that aresituated on the respective outer faces (11, 11′) of the two actuatingbelts (1, 1′), on the one hand, and on the respective longitudinal faces(20, 20′) of the studs (2, 2′) and the sections (5, 5′) of therespective inner faces (10, 10′) of the two actuating belts (1, 1′)separating those studs, on the other hand, are identical.
 11. Linearactuator according to claim 9, characterized in that each of therespective front transverse active faces (7, 7′) and rear transverseactive faces (8,8′) of the studs (2, 2′) of the actuating belts (1, 1′)has a double curvature.
 12. Linear actuator according to claim 9,characterized in that the front and rear transverse active faces (7, 7′;8, 8′) of the studs (2, 2′) comprise a double shoulder (9) forming anabutment so as to prevent any transverse sliding of the adjacent studs(2, 2′) relative to one another when the two actuating belts (1, 1′) areassembled integrally.
 13. Linear actuator according to claim 9,characterized in that the drive members (3) are constituted by a casing(12) containing two rotary pinions, that is, a drive pinion (13) and adriven pinion (13′) which engage one another whilst driving two endlesscaterpillar-type bands (18, 18′) mounted on one side and on the otherside of the actuating belts (1, 1′), respectively, and equipped on theirouter faces with teeth (21, 21′) which cooperate with the teeth (4, 4′)situated on the outer faces (11, 11′) of those belts (1, 1′), whilstbeing fitted between those teeth, so as to translate the belts whilstsqueezing them against one another so that their facing studs (2, 2′)engage one another.
 14. Linear actuator according to claim 13,characterized in that the two rotary pinions (13, 13′) are extendedcoaxially by respective toothed extensions (15, 15′) of smallerdiameter, cooperating with respective idle auxiliary gears (17, 17′) ofthe same diameter so as to drive the endless caterpillar-type bands (18,18′).
 15. Linear actuator according to claim 13, characterized in thatthe casing (12) of the drive members (3) contains at least a pair ofpositioning rollers (22) having axes Y-Y′ substantially perpendicular tothe axes X-X′ of the rotary pinions (13, 13′) and engaging, on one sideand on the other side of a linear portion of the actuator defined by thetwo integrally assembled actuating belts (1, 1′), against the side faces(6, 6′) of the studs (2, 2′) of those belts (1, 1′).